fix(stdlib): rename total var -> tot (#135 slice 4) (#168)

#135 slice 4 — the triage hypothesised a block/statement LR ambiguity
for testing.affine:302 / math.affine:354.  Precise isolation disproved
that: every minimal block/stmt shape parses.  The real cause is
keyword-as-identifier (slice-6 class): `total` is the `TOTAL` reserved
keyword (totality marker, `total fn`), so `let total = …` fails to
parse.  `let total = 0.0; …` fails; `let tot = 0.0; …` parses.

Rename the `total` *variable* -> `tot` in math.affine `mean`/
`sum_float` (also `let mut`, they reassign in a loop) and testing.affine
`bench`.  The `total_time` record field is a different identifier
(`total` only when bare) and is left unchanged; string-literal "total"
text untouched.  Pure stdlib rename — zero grammar/compiler risk.

Effect: math.affine PARSE 354 -> RESOLVE; testing.affine PARSE 302 ->
TYPECHECK (both clear the parse wall, advance to distinct deeper
defects).  traits.affine:124 is unrelated (`while let` pattern binding)
— a genuine separate construct, still tracked.  Suite unaffected
(stdlib-only).

Advances #135. Refs #128, #135.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

stdlib/math.affine

@@ -351,18 +351,18 @@ fn mean(values: [Float]) -> Float {
   if n == 0 {
     return 0.0;
   }
-  let total = 0.0;
+  let mut tot = 0.0;
   for v in values {
-    total = total + v;
+    tot = tot + v;
   }
-  total / to_float(n)
+  tot / to_float(n)
 }
 
 /// Sum of a list of floats
 fn sum_float(values: [Float]) -> Float {
-  let total = 0.0;
+  let mut tot = 0.0;
   for v in values {
-    total = total + v;
+    tot = tot + v;
   }
-  total
+  tot
 }

stdlib/testing.affine

@@ -299,11 +299,11 @@ fn bench(f: () -> (), iterations: Int) -> BenchResult {
     i = i + 1;
   }
 
-  let total = time_now() - start;
+  let tot = time_now() - start;
   {
     iterations: iterations,
-    total_time: total,
-    avg_time: total / (iterations + 0.0)
+    total_time: tot,
+    avg_time: tot / (iterations + 0.0)
   }
 }